GT350R brake upgrade kit and rear wheel offset

[BluePonyGT]

Ok kids - I did it. My wallet is practically empty but I got the kit in hand, and as soon as the weather improves this spring I'm going to get this going.

One big question that I'm looking at is rear wheel offset needed when this is done.

I'm currently sporting a project 6GR 19x11 rim in the rear with +50mm offset. That's a lot - there's enough room for me to fit my finger in between the tire and the brake bracket on the inner part of the "tub". Plenty of space for the rotors and all the shenanigans I'm about to be up to however, so I'm not worried about that.

I found this article regarding wheel specs for the GT350R: https://www.mustang6g.com/forums/threads/official-gt350-wheel-specs.40696/

The rear 19x11 rim has a +62mm offset? I'm worried that my rims are going to push out a centimeter or more when those new rotors go on from where they are now. They currently sit flush with the fender with the stock GT brakes. If the mounting surfaces for the existing wheels get pushed out then I definitely will end up with too much poke.

So should I start saving for new rims to support a higher positive offset?

I'm not worries about the fronts at all. They're currently 19x10 with a +35mm offset. That's still within range of the GT350R numbers.

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[NightmareMoon]

GT350s and GTs use the same wheel offset fit in the rear I believe. The fronts are a little different since the 350 has slightly wider front fenders. I think the mating surfaces for the hub/wheel are the same place between the two cars, despite the different parts.

the stock 350 rear wheel may be an ET62 which would make aense because Ford doesn’t like to push them out as flush to the fender as the aftermarket does. 10mm offset is only 0.4”

That 11 ET52 will be borderline poke if you run stock (mild) rear camber, but its a great fit if you dial a small amount of extra rear camber. Even with stock camber it will be fine, its just aggressive.

enjoy!

 

[Kellys69z]

You will have to go to the +62 offset. Front is the same hub flange to hub flange. Rear is about 20mm wider. You also have to use the gt350 rear knuckles or modify yours. I modified mine and made bushings for the smaller caliper bolts. The mounting holes for the abs sensor is moved out for the parking brake adapter

 

[BluePonyGT]

You will have to go to the +62 offset. Front is the same hub flange to hub flange. Rear is about 20mm wider. You also have to use the gt350 rear knuckles or modify yours. I modified mine and made bushings for the smaller caliper bolts. The mounting holes for the abs sensor is moved out for the parking brake adapter

Thanks that's what I was concerned about. I may be in the market for new rear rims. +50mm offset on the existing rims with the GT setup puts those rims right at the edge of the fender. Looks great, but this kit is going to push them out past the fender.

Also, the kit comes with the GT350R knuckles. There's some tapping to do for the speed sensor bolt, etc., but it has brackets for the parking brake cables, etc. I was surprised to see how thorough this kit actually is, but it's $$$.

 

[Brazos609]

You need to use GT350 fitment 11" rims. I've got a GT350 brake kit to install myself and I planning on getting LMR SVE R350 11" rear rims to use with it.

 

[BluePonyGT]

You need to use GT350 fitment 11" rims. I've got a GT350 brake kit to install myself and I planning on getting LMR SVE R350 11" rear rims to use with it.

I think I have this figured out. I bought the GT rims from Project6GR which aren't set up for the offset I need. They have R-spec wheels for the GT350 that has a +56mm offset but that sounds like it's not enough for the GT fenders. It assumes I have the other body style.

The existing 19x10 front rims have a +35mm offset. They're calling for a 19x11 front rim with a +24mm offset. That's clearly less than what I have, but too wide of a tire for the fenders.

Your rims have the following specs:

Wheel Specs
Front:
Size: 19x10
Backspace: 6.29"
Offset: +20mm
Weight: 25.5lbs

Rear:
Size: 19x11
Backspace: 8.36"
Offset: +60mm
Weight: 24.2lbs

That's probably better for a GT moving to a GT350R brake setup.

Oh and Project6GR is trying to tell me that 19" rims won't be good enough. I have to go to 20". That's not what ford performance told me at all.

 

[D Bergstrom]

So you bought the M-2300-Y kit? Years ago I did a bunch of research on that kit because I was intending to buy it for my 2017 GT. Never did, but my research led me to believe that front off set doesn’t matter, the GT350 brakes do not add or subtract anything from the track width. Your current 35mm offset front rims will work just fine. You probably would not want to go much lower on front offset, since the 350’s have wider front fenders to deal with extra width.

The rear GT350 hubs get pushed out just over 1/4” on each side due to the ebrake setup. So your current 50 mm offset rear wheels would be an effective 43 mm once the 350 brakes are installed. Depending on tire size, pushing the rear wheels out that extra 1/4” may or may not be an issue.

This is strictly for offset, caliper clearance is a whole other issue.

That being said, there have been a few GT350 owners that have used a 19x11, 50 offset square setup on their cars, (spacers/longer lugs on the front, rears bolted straight on. ) and the rears fit with no issues, but pretty sure they were all running 305/30 tires all around. I actually had a set of 4 SVE SP2’s 19x11’s that I sold to a guy with a GT350 and he was going to run them as a square setup. As far as I know, he didn’t have any issues., but he was also planning on 305/30 tires. As far as I know, rear fenders are all the same, 350, GT, Ecoboost.

Not sure why 6gr is telling you 20” wheels are needed. They sell a 19x11, 19x11.5 specific setup for the 350.

Doug

 

[Kellys69z]

This is with 19x11 +62 and 325’s and 19x10 +37 with 295’s. The front is just inside the lip and the rear have about 1/8 poke. You have to be careful on 19” wheels and caliper clearance I was told they would clear, but had to do some grinding on the calipers.

 

[Kellys69z]

This is an oem front 19x10 gt350 wheel it has about 1/2”-5/8” poke with. 295.

 

[BluePonyGT]

So you bought the M-2300-Y kit? Years ago I did a bunch of research on that kit because I was intending to buy it for my 2017 GT. Never did, but my research led me to believe that front off set doesn’t matter, the GT350 brakes do not add or subtract anything from the track width. Your current 35mm offset front rims will work just fine. You probably would not want to go much lower on front offset, since the 350’s have wider front fenders to deal with extra width.

The rear GT350 hubs get pushed out just over 1/4” on each side due to the ebrake setup. So your current 50 mm offset rear wheels would be an effective 43 mm once the 350 brakes are installed. Depending on tire size, pushing the rear wheels out that extra 1/4” may or may not be an issue.

This is strictly for offset, caliper clearance is a whole other issue.

That being said, there have been a few GT350 owners that have used a 19x11, 50 offset square setup on their cars, (spacers/longer lugs on the front, rears bolted straight on. ) and the rears fit with no issues, but pretty sure they were all running 305/30 tires all around. I actually had a set of 4 SVE SP2’s 19x11’s that I sold to a guy with a GT350 and he was going to run them as a square setup. As far as I know, he didn’t have any issues., but he was also planning on 305/30 tires. As far as I know, rear fenders are all the same, 350, GT, Ecoboost.

Not sure why 6gr is telling you 20” wheels are needed. They sell a 19x11, 19x11.5 specific setup for the 350.

Doug

This is actually a huge help. Like a dummy I completely forgot about tire size.

I'm running 285 35R19 in the front and a whopping 325 30R19 in the rear. I might be able to drop down to a 305 35R19 in the rear and avoid the extra poke and just go with a new set of tires. I have plenty of fender in the front. It's the rear that is dead on flush right now with that +50mm offset, but again, running an extra wide tire at 325.

Also, I did a complete suspension upgrade with steeda during the pandemic so the car is sitting 1" lower than it was on progressive springs. That combined with the swapped control arms I get a TINY bit of rub on the inner fenders when I turn the wheel all the way over one way or the other, so the wheels can stand to go out a touch.

Finally, I have NO IDEA why they're insisting that the 19" rim won't work with this kit. They didn't even let me tell them what rim I had.

So...when I start this I'm going to mock up the front caliper and rotor, then put the rims on and see where I am. If I have clearance issues I REALLY don't want to grind these calipers and I'll have to judge based on where the contact is what to do. 20" rims are really not a direction I want to go.

 

[BluePonyGT]

This is with 19x11 +62 and 325’s and 19x10 +37 with 295’s. The front is just inside the lip and the rear have about 1/8 poke. You have to be careful on 19” wheels and caliper clearance I was told they would clear, but had to do some grinding on the calipers.

Your setup in the rear is from the outside almost exactly where mine are sitting before I even touch anything. My 19x11 rims have +50mm offset and have a 325/30R19 tire on them, and it looks identical to that. So based on the extra 1/4" of poke with the existing setup if I go with a narrower tire like a 305 I may end up roughly in the same spot on the existing rim. Maybe...

 

[Red65]

So what’s the general consensus for running square tire sizes on a 19 or 20 inch rim with the GT350 brakes on a GT? I’ve got the base GT brakes and the GT350 setup is something I’ve entertained, but I’d rather not run staggered tire sizes

 

[BluePonyGT]

So what’s the general consensus for running square tire sizes on a 19 or 20 inch rim with the GT350 brakes on a GT? I’ve got the base GT brakes and the GT350 setup is something I’ve entertained, but I’d rather not run staggered tire sizes

This will have to be a process of experimentation unfortunately. I did want to go staggered - that was the plan all along, but I didn't count on having issues with clearance on the 19" rims I have. Plus I have to be honest - I didn't even think about wheel offset in the back.

So I have potentially a couple of issues:
* Front brake clearance on the 19x10 rims i have in front. I really hope not, but we shall see. Everything I researched up to this point had no issues with 19" rims so this is a new one on me. I won't know until I mock up the fronts and take a look at what I may have to do.
* Offset pushes the rims out in the back too far. I may have to fix this by going with a different size tire on my 19x11 rims.

However, if I have clearance issues in the front It'll either put me on a path to find the right 19's that will fit or I have to move to 20" rims, which I do NOT want to do. That will leave me with some rather terrible choices: create clearance myself by modifying the calipers (yuck) or find new 19" rims that will work.

A square setup? We may have to go over to the GT350 forums and find out what rims/tires people are running.

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